Chapter 8, Problem 63P

Interpretation Introduction

Interpretation: The structure of compound with boiling point of $78°\text{C}$ should be chosen.

Concept introduction:An empirical formula gives the simplest whole number ratio of atoms of each element present in a molecule. Molecular formula tells the exact number of atoms of each element present in a molecule.

The steps to determine the empirical formula of a compound are as follows:

Divide mass of element by its molar mass to convert mass to moles as follows:

  $\text{Amount}\left(\text{mol}\right)=\left(\text{Given mass}\left(\text{g}\right)\right)\left(\frac{1\text{ mol}}{\text{No}\text{. of grams}}\right)$

The number of moles thus calculated are written as the subscript of the element’s symbol and this results in a preliminary formula for the compound.

In order to convert the moles to the whole number subscripts each subscript is divided by the smallest subscript.

Sum of product of the molar mass of each element times number of corresponding atoms results in empirical formula mass.

The formula to calculate whole number multiple is as follows:

  $\text{Whole}-\text{number multiple}=\frac{\text{Molar mass of compound}}{\text{Empirical formula mass}}$

The product of this the whole number with the subscript of each element results in molecular formula.